Strain insulator



Jan. 3, 1933. HAWLEY 1,892,888"

STRAIN INSUIJATOR Filed March 25, 1929 r {f I7 gnuc'nfot Km/ A. Hawlcy Patented Jan. 3, 1933 PAT-Eur FFI KENT A. HA'WLEY, OF BALTIMORE, MARYLAND, ASSIGNOR TO LOCKE INSULATOR' I CORPORATION, OF BALTIMORE, MARYLAND, A CORPORA'I'ION OF MARYLAND STRAIN insurnron Application filed March 25, 1929. Serial No. 349,802.

sulator which may be employed as a heavy duty strain insulator for suspension, guy or other purposes which may suggest themselves.

An important object of the invention is to provide a strain insulator embodying a m dielectric body of peculiar shape whereby it will have great mechanical as well as electrical strength notwithstanding that it is made of hollow form for the sake of lightness and to enable use to be made of the insulating properties of air.

Another object of the invention is to provide an insulator embodying a single dielectric member, preferably of porcelain, together with an arrangement of cooperating metallic elements which will insure great electrical as well as mechanical strength in addition to thermal efficiency.

A further object is to provide an insulator which will be simple, comparatively inex- 5 pensive, eflicient and durable in service, and

a general improvement in the art.

Figure 1 is a view partly in side elevation and partly in longitudinal section showing the insulator, and

Figure 2 is a cross sectional view taken on the line 2-2 of Figure 1.

Referring more particularly to the drawing, I have shown the insulator as comprising a dielectric body 7 preferably of porcelain formed, glazed and fired in the usual manner. This body 7 must have considerable strength for which reason I have disclosed it as of double frusto-conical shape, that is to say it has its largest diameter at the center with both ends tapering off, the body being, moreover, preferably circular in cross section throughout so that the strains coming upon it will be uniform. The body is likewise shown as of shell-like form or hollow and the thickness of the wall will of course vary in accordance with the other dimensions all of which would be governed by the demands of the particular installation. Surrounding the central or largest part of this body is a metallic member 8 including a ring or band portion 9 and outstanding flanges 10 thereon. The band portion is shown as secured upon the dielectric body by cement 11 and, in accordance with well established insulator practice, the exterior of the porcelain body'may be sanded or roughened at the area engaged by the cement so as to increase the holding power thereof.

The ends of the dielectric body are'open and carry upper and lower caps 15 and 16 which may be identical in construction, which constitute closures for the ends, and which are preferably held by cement 17 applied in a well known manner. The end portions of the body may also be roughened or sanded to give the cement a better grip. Extending axially of the body is a bolt or rod 18 which has both ends projecting consider ably beyond the caps 15 and 16, one end having an eye 21, the other endbeing threaded and carrying a nut 19, and the intermediate portion having a flange 20, the nut and flange engaging against the caps 15 and16 in clamping relation thereto.

The outstanding flange 10 is apertured at 14: for the passage of elongated rods 24 which in turn carry a metallic end member 25 which may be formed or otherwise equipped with an eye 26, clevis or the like for suspension or connecting purposes.

When the insulator is constructed as shown, it is apparent that it is used in identically the same manner as other strain insulators and no further explanation in regard thereto should beconsidered necessary.

The structure possesses particular advantage from an electrical viewpoint. It should be remembered that while this type of insulator is adapted for low frequency power that the air should be the principal insulator when working with radio frequencies as the energy loss will be proportional to the distance of the rod from the supporting base and proportional to the specific inductive capacities, or in other words .the dielectric constants of the insulating media. The air being the true insulator, rather than the porcelain, has a specific inductive capacity of unity whereas that of the porcelain isapproximately five. In using an insulator of this character, design or shape, rather than one of a cylindrical or other shape, the power loss due to induction between parts will be the minimum.

While I have shown and described the preferred embodiment of the invention, it should be understood that the disclosure is merely an exemplification of the principlesinvolved as the right is reserved to make all such changes in the details of construction as will widen the field of utility and increase the adaptability of the device provided such changes constitute no departure from the spirit of the invention or the scope of the claims hereunto appended.

Having thus described the invention, I claim:

1. A strain insulator comprising a double ended frusto-conical hollow dielectric body ofmaximum diameter at its center and open at its ends,a metallic collar extending about and secured to the maximum diameter central portion of said body, metal caps closing the ends of the body, a tie bolt extending axially through the body and confining said caps thereto, an attaching member located in spaced relation to one end of the body, and a plurality of elongated connecting elements connected with said attaching member and said collar.

2. A strain insulator comprising a double ended frusto-conical hollow dielectric body having its maximum diameter midway of its ends, metal caps secured upon the ends of said body and closing the same, a tie bolt extending axially through the body and through said caps and having one end formed as an attaching member, a collar surrounding and secured to the intermediate portion of said body and having an outstanding flange, a second attaching member located at a distance from one end of the body, and a series of elongated connecting elements arranged circumferentially of said collar and secured to the flange thereof at one end and secured at their other ends to the second named attaching member.

- In testimony whereof I aflix my signature.

KENT A. HAWLEY. 

